Conventionally, as for a hole plug, there is, for example, Patent Document 1. In this conventional technology, the hole plug comprises a cylindrical outer circumferential wall face extending downward from an inner circumferential edge portion of a flange portion covering a hole edge circumferential face of an attachment hole drilled in the attachment member; and an inner circumferential wall face folded inward from a lower end of the outer circumferential wall face, and expended upward. Then, engagement claws formed in a plurality of engagement protrusions radially formed on the outer circumferential wall face engage with the attachment hole.